In the field of manufacturing processes of semiconductor elements the semiconductor elements are often processed on a wafer scale. With the proceeding of the technology often so called thin film wafer are used even in the field of power modules, i.e. modules comprising semiconductor elements or chips designed for withstanding high voltages or currents. These power modules are used in rectifiers or inverters in the automotive sector, for example. For reducing the thickness of the chips, e.g. transistors or diodes, the bulk of the wafer itself is often used for providing or defining the inverse or block voltage. As a general rule each 1 micrometer of thickness corresponds to 10 V inverse voltage.
However, due to the fact that the bulk or thickness of the wafer itself and not of an (epitaxial) deposited layer defines the block voltage, variations in the thickness of the wafer directly correspond to a variation of the blocking voltages and thus directly effects the performance of the electronic element or component. Therefore, the total thickness variation (TTV) of the bulk wafer should be as low as possible. Therefore a plurality of complex measures are performed in the prior art to reduce the TTV.